| outline the light dependent reaction | light energy is absorbed by the chlorophyll in PSII causing electrons to be excited and boosted to a higher energy level
the electrons are picked up by an electron acceptor
the electrons move down an ETC through a series of redox reactions to PSI
as the electrons move down the ETC, they release energy which is used for chemiosmosis
The electrons lost in PSII are replaced by the photolysis of water
oxygen is given off as a waste gas and H+ ions and electrons are used to form NADPH and ATP |
| where does the light dependent reaction occur? | happens in the thylakoid membrane |
| outline chemiosmosis | hydrogen ions from the stroma are actively pumped into the thylakoid lumen
energy from the electron transfer chain is used to do this
this forms an electrochemical gradient because of the difference in concentration of H+ ions
the H+ ions in the lumen flow through ATP synthase by facilitated diffusion forming ATP and NADPH which will be used in the light independent reaction |
| Outline the Light independent reaction | RUBP and CO2 combine to form a 6 carbon intermediate that immediately divides to form GP (3C)
the RUBP + CO2 reaction is catalysed by rubisco
NADPH and ATP are then used to catalyse the conversion of GP into GALP (3C)
some molecules of GALP combine to form glucose (6C) whilst the rest are used to regenerate the RUBP using ATP |
| Light independent reaction | also known as the Calvin cycle
occurs in the stroma of the chloroplast
uses CO2, NADPH and ATP
products are glucose, NADP+ and ADP+Pi
has three stages: carbon fixation, reduction and regeneration |
| structures of the chloroplast | thylakoid
stroma
lamellae
grana/granum
inner membrane
outer membrane
intermembrane space |
| structures of the thylakoid | thylakoid lumen
thylakoid membrane
photosystems I and II
chlorophyll
ATP synthase
electron carrier proteins |
| photophosphorylation | the conversion of ADP into ATP using energy from sunlight |
| process of photolysis | energy from sunlight is used to break the bonds between the hydrogen atoms and the oxygen atom in a water molecule
hydrogen is then further split into H+ ion and electrons |
| what is NPP? | net primary productivity
the difference between energy fixed by autotrophs and their respiration |
| what is GPP? | gross primary productivity
the energy transferred to primary consumers |
| equation combining GPP, NPP and respiration | NPP = GPP - R |
| define primary productivity | the rate at which energy is converted into organic substances by photosynthetic and chemosynthetic autotrophs |
| define ecosystem | all the biotic and abiotic factors of a particular area |
| define community | all of the populations of all the organisms living in a particular habitat at a particular time |
| define population | all of the organisms of a particular species living in a particular habitat at a particular time |
| define habitat | the place where an organism lives |
| define biotic | the living elements of a habitat |
| define abiotic | the non-living elements of a habitat |
| what is the distribution and abundance of a habitat controlled by? | biotic and abiotic factors |
| define niche | the particular role of a species in a habitat |
| what does a niche consist of? | biotic and abiotic interactions with the environment |
| what does species distribution and abundance in a habitat depend on? | the number and type of ecological niches available within the habitat |
| what is the niche concept? | states that only one organism can occupy each niche at a given time
if two or more species have a niche that overlaps, the best adapted will outcompete the others to survive and reproduce |
| define succession | the change in species inhabiting an area over time |
| what is succession brought about by? | changes to the environment made by organisms colonising it by themselves |
| what is primary succession? | occurs when an area previously devoid of life is first colonised by communities of organisms |
| what secondary succession? | occurs with existing soil that is clear of vegetation |
| what is humus? | the organic component of soil |
| what are pioneer species? | species that first colonise an ecosystem
they are adapted to survive in harsh conditions
they can break down rocks and hold together sands |
| what happens when organisms die? | they are decomposed by microorganisms
this adds humus leading to soil formation
over time more decomposed organisms adds more minerals to the soil
this allows for more varied and complex organisms to survive |
| what is a climax community? | the most productive, self-sustaining and stable community that an environment can support, usually with only one or two species |
| stages of succession | pioneer species
primary succession
secondary succession
climax community |
| calculate efficiency of biomass and energy transfers between tropic levels | % efficiency = (energy from a lower trophic level/energy from a higher trophic level) X 100 |
